The present disclosure relates generally to optical lens systems, and, more particularly, relates to stereoscopic objective lens designs with a zoom function adapted for use in stereo video endoscopes.
Medical endoscopes are widely utilized to view internal regions of the human body during diagnostic, surgical, and other medical procedures. Endoscopes typically include a long, thin, rigid or semi-rigid optical cylinder affixed to a viewing mechanism. The cylinder is sufficiently narrow to be inserted through a small opening in the body, which may be natural or surgical. When the endoscope is inserted and positioned for use, an image of the object being viewed is formed at an inserted end of the endoscope by an objective lens. The image passes through a series of relay lenses down the cylinder to an eye lens or video camera at a viewing end of the endoscope.
In recent years, researchers have attempted to improve the imaging available through endoscopic devices by developing stereoscopic video endoscopes. These endoscopes present an apparently three-dimensional image on a video monitor. The stereoscopic effect is created by producing two optical images—a left image and a right image—through the endoscope. The left and right optical images are presented by the endoscope to left and right image sensors, which may be charge-coupled device (CCD) cameras or other image sensing devices. The sensing devices convert the left and right optical images into left and right video images which are then presented as alternating left-right images on a monitor, at a switching rate higher than the flicker-sensing limit of the human eye, so that observed images appear flicker-free.
In existing stereoscopic video endoscopes, the object position, which corresponds to the distance from the end of the endoscope to the area of interest, is fixed at the location corresponding to the stereo plane designed into the endoscope. Any departure from this plane causes differential results in the stereoscopic effect. Nevertheless, surgeons commonly change the distance to the object of interest when using a stereoscopic video endoscope. For example, to see more area, the surgeon may pull the endoscope away from the object of interest, and conversely to increase the magnification, the surgeon may move the endoscope closer to the object of interest. It would be desirable to have a stereoscopic video endoscope that provides the ability to change the magnification without moving the endoscope.